Effect of temperature and substrate on whole body cortisol and size of larval white sturgeon (Acipenser transmontanus Richardson, 1836)

White sturgeon (Acipenser transmontanus Richardson, 1836) larvae were reared at two temperatures (13.5 or 17.5 degrees C) with or without gravel as a substrate to examine the effect of rearing environment on growth and whole body cortisol, an index of stress (initial weight 23.4mg; four replicate tanks per treatment). Larvae were sampled 8, 16, and 24days post-hatch. Larvae were larger when reared with substrate and at warmer temperatures. For whole body cortisol, a significant age by temperature interaction was observed with the highest values on day 16 for larvae from warm water treatments. Larvae reared in gravel consistently showed significantly lower whole body cortisol than larvae reared without substrate. In response to mechanical agitation, there was a significant effect of time following disturbance. Increased growth and reduced stress hormone levels make substrate rearing of yolksac larvae an important technique for enhancement efforts in artificial and natural environments. The positive effects of temperature on growth, however, with higher whole body cortisol, suggest that larval white sturgeon development may be better at cooler temperatures.